International media have flocked to Thailand following last Monday's deadly shrine bombing, which cut down 20 people, mostly Asian tourists, in the heart of one of Bangkok's busiest shopping districts and wounded scores more.

No arrests have been made with the police scrambling to identify the perpetrators of an attack that has sent shockwaves through the country's vital tourist sector.

The Foreign Correspondents' Club of Thailand criticised Kwan's arrest, adding they had been told the photographer would be tried in a military court.

"He is being charged with possessing an illegal weapon, which carries a prison sentence of up to five years, and which will be tried in a military court," the FCCT said in a statement.

"Body armour and helmets used by journalists are not offensive weapons and should not be treated as such," the group added.

Since seizing power in a coup last year, Thailand's junta have ramped up use of military courts.

Thai police did not respond to requests for comment Monday morning.

Basic personal protection equipment commonly used by media around the world such as gas masks, ballistic vests and helmets are classified as weapons under Thailand's Arms Control Act and have to be licensed.

But attempts by media groups over the years to seek permission from authorities to carry such items have fallen on deaf ears despite the country's long history of deadly street protests and a festering Muslim insurgency in the deep south.

Until now, the ban on civilians and journalists carrying unlicensed equipment had largely been ignored.

During Thailand's regular bouts of often violent street protests, demonstrators on both sides of the country's political divide have been seen donning ballistic vests and helmets.